Windows Spooler Service Suspicious Binary Load

Description

Detect DLL Load from Spooler Service backup folder. This behavior has been observed during the exploitation of the Print Spooler Vulnerability CVE-2021-1675 and CVE-2021-34527 (PrinterNightmare).

Query · sigma

selection:
  Image|endswith: \spoolsv.exe
  ImageLoaded|contains:
  - \Windows\System32\spool\drivers\x64\3\
  - \Windows\System32\spool\drivers\x64\4\
  ImageLoaded|endswith: .dll
condition: selection

Known false positives

  • Loading of legitimate driver
Raw source Windows Spooler Service Suspicious Binary Load · Sigma
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Published by SigmaHQ/sigma ↗, licensed under Detection Rule License 1.1 ↗. Reproduced here unmodified. 
title: Windows Spooler Service Suspicious Binary Load
id: 02fb90de-c321-4e63-a6b9-25f4b03dfd14
status: test
description: |
    Detect DLL Load from Spooler Service backup folder. This behavior has been observed during the exploitation of the Print Spooler Vulnerability CVE-2021-1675 and CVE-2021-34527 (PrinterNightmare).
references:
    - https://web.archive.org/web/20210629055600/https://github.com/hhlxf/PrintNightmare/
    - https://github.com/ly4k/SpoolFool
author: FPT.EagleEye, Thomas Patzke (improvements)
date: 2021-06-29
modified: 2022-06-02
tags:
    - attack.persistence
    - attack.privilege-escalation
    - attack.execution
    - attack.stealth
    - attack.t1574
    - cve.2021-1675
    - cve.2021-34527
    - detection.emerging-threats
logsource:
    category: image_load
    product: windows
detection:
    selection:
        Image|endswith: '\spoolsv.exe'
        ImageLoaded|contains:
            - '\Windows\System32\spool\drivers\x64\3\'
            - '\Windows\System32\spool\drivers\x64\4\'
        ImageLoaded|endswith: '.dll'
    condition: selection
falsepositives:
    - Loading of legitimate driver
level: informational

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